Fibromyalgia syndrome (FMS) is estimated to affect about 5% of all Americans, is the third most common rheumatic condition, and accounts for 15 to 40% of referrals to rheumatologists. FMS is five times more common in women than men and those seeking health care are most likely between 40 to 60 years. The mechanisms central to primary FMS remain elusive but the main postulates include central changes manifesting as physical sleep arousal, hypothalamic-pituitary hormone, and serotonergic disturbances. These central changes are postulated to create end organ and tissue peripheral changes, particularly in muscle and the host defense (inflammatory/immune) system, that give rise to signs and symptoms of fatigue, non-restorative sleep, amplified muscle pain, somatic and psychological distress symptoms and inflammatory or immune changes like hyperemia, NK cell activity suppressions and altered T cell activation markers. The aims of this study in 2 groups of women with FMS (with and without major depression) compared to a pain-free control group, are to: 1. describe and compare central changes including: a) aroused physical sleep; b) hormone patterns (amplitude, mesor, acrophase, area under the curve of nighttime GH, PRL, ACTH & MT); and c) serotonin deficit (platelet serotonin content): and peripheral changes including: d) serotonin deficit; e) hypocortisolemia; d) inflammatory/immune function. As well the aims are to describe the relationships among aroused physical sleep variables, the circadian hormone pattern variables, and serotonin variables and the FMS and other symptoms and the between the nighttime hormone exposure (area under the curve) and inflammation/immune function variables. Further to describe the daily symptom severity over time (30 days) and the activity levels and 24 hour sleep/wake patterns. A total sample of 90 women, ages 35 and 60 years, will be recruited for this a cross-sectional, repeated measures, 3-group comparative design. Sixty women (30 with and 30 without major depression) meeting the criteria of the American College of Rheumatology 1990 for fibromyalgia will be recruited through the Chronic Fatigue Clinic at Harborview Medical Center and 30 pain-free healthy women will be recruited from the community. They will be assessed through home monitoring and in the sleep laboratory from 8 p.m. to 8 a.m. over three nights (one for adaptation, one for sleep measures, one for blood draws). Women will keep daily diaries for two weeks to self-report somatic and psychological symptoms and sleep quality over time. They will wear an activity monitor for 3 consecutive days during the follicular phase of their menstrual cycles (if cycling) as a measure of sleep and wake and overall activity levels. Laboratory measures will include standard somnography for sleep and serial venous blood draws for nighttime hormone assays.